Copper Coating Analysis of Pennies

Organic Acids and Effects on Cleaning Pennies. Daniel and Carolyn. Penny cleaning by use of organic acids is a common yet not entirely understood process. For example, lemon juice is commonly used as a cleaner. Pennies were left in distilled acid solutions to allow possible processes such as acid-base reactions, chelation, and dissolving to clean the pennies fully. The different acids that were tested resulted in cleaner pennies. Different compounds were also tested and compared as potential penny coatings, yet no compound produced similar results when reacted with citric acid. Thus, pennies must contain other compounds on their outer layers. However, both citric acid and oxalic acid were shown to clean pennies better than distilled water. Better understanding of the process could be used to make penny cleaning more efficient and effective, allowing more coins to stay in circulation and reducing excessive outputs of the U.S. mint. Key words: chelation, acid-base reaction, organic acids, citric acid, copper, penny

Our experiment had three parts:







Here is a description of the lab process: